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Optical fibers have been used for detection of analytes in aqueous and vapor phases by assessing changing light transmission parameters resulting from biomolecular interactions occurring on fiber surfaces. The primary objective of this study is to refine the optical fiber design by tapering the fiber to modify the light path for enhanced detection of vapor phase analytes at very low concentrations, particularly volatile organic compounds (VOCs). The typical light path through a single mode fiber with cladding results in low loss of light from the fiber. Tapering the fiber removes the cladding, thins the diameter of the fiber core, and results in net loss of light from the core of the fiber. Lost light (photons) exists as a wave along the surface of the tapered fiber. Molecular binding events on the surface of the taper result in disruption of the light path which is measurable as a change in refraction/intensity.Single mode optical fibers have been tapered from 125 microns to 10-15 microns in diameter via heat treatment and pulling of fibers. Tapered regions serve as the sensing interface, such that the light propagating through/around the fiber can interact with molecules tethered to the surface. Tapered regions will be functionalized with biomolecules for capture/detection of analytes in both aqueous (antibody) and vapor phase (DNA, peptide recognition molecules). Interaction of recognition molecules with analytes will cause a change in the molecular structure at the tapered surface. We posit that these changes will affect light passing through the fiber and will result in a characteristic spectral fingerprint indicative of the analyte. Future work will focus on refinement of surface chemistry to maximize molecular interactions for detection of low concentrations of analytes. We envision the use of tapered optical fibers in array format for detection of multiple analytes in complex samples.